Ixxii 



Achromatic Eyepieces" in Nicholson's Journal for 1806 ; and seven year3 

 afterwards he published a separate " Treatise on new Philosophical Instru- 

 ments for various purposes in the Arts and Sciences." In 1816, while 

 repeating some experiments of Biot with a glass trough, he noticed that 

 peculiar method of reflection which is the principle of the Kaleidoscope ; and 

 no sooner was this pretty instrument before the public than it became 

 marvellously popular, and that not only as a toy for old and young, but 

 large expectations were raised of its usefulness to the artist and designer of 

 patterns. We are also indebted to him for many other ingenious contri- 

 vances for micrometers, burning-glasses, &c, and his writings frequently 

 contained the germs of future inventions. Hence it is not easy to deter- 

 mine his precise share of merit in such appliances as the lenticular stereo- 

 scope, or the polyzonal lenses used in lighthouses. In regard to the latter, 

 however, it may be safely maintained that while the chief credit of elaborating 

 the dioptric system of illumination must be given to Fresnel, the persistent 

 advocacy of Brewster materially contributed to its adoption on the shores of 

 our own island. 



In addition to the treatises already mentioned he wrote several distinct 

 works of a biographical character : — the Memoirs of Sir Isaac Newton, 

 Euler's Letters and Life, and the Martyrs of Science, viz. Galileo, Tycho 

 Brahe, and Kepler. Nor must be omitted his letters on Natural Magic, 

 and his ' More Worlds than One, the Creed of the Philosopher, and the 

 Hope of the Christian.' 



Sir David's anonymous writings were nearly as numerous as those to 

 which his name was attached, and they spread over a wider range of sub- 

 jects. The elaborate treatises on Optics in the Edinburgh Encyclopeedia 

 and in the recent editions of the Encyclopaedia Britannica are both from his 

 pen, and to each he contributed the articles on Hydrodynamics and Elec- 

 tricity. In the older work he also wrote on Astronomy, Mechanics, Mi- 

 croscopy, and Burning instruments, while in the later work he turned his 

 attention among other subjects to that of photography. 



To the Edinburgh Review he contributed twenty-eight articles, which 

 are comprised between the Nos. LVII. and LXXXI. They include bio- 

 graphical notices of such men as Davy and Watt ; reviews of such philoso- 

 phical works as Whe well's ' History and Philosophy of the Inductive 

 Sciences,' Mrs. Somerville's ' Connexion of the Physical Sciences/ Lord 

 Brougham's ' Discourse on the Study of Natural Philosophy,' and even 

 Compte's ' Philosophic Positive: ' they pass from Buckland's Geology or 

 Daguerre's photogenic drawings to the lighter subjects of deer-stalking or 

 salmon-fishing; they follow Sir James Ross or Sir George Back in their 

 arctic researches, and describe the British lighthouse system or the phe- 

 nomena of thunder-storms. 



To the Quarterly Review he seems to have contributed five articles, and 

 in them he gives his estimate of works by Babbage, Herschel, and Aber- 

 crombie ; while the subjects he treats are as wide apart as the production 



